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A physical-mathematical model of oscillations of unbalanced vibrators of a pneumatic sorting table as non-stationary oscillations of an impulse-loaded round plate with various options for fixing its contour has been built. The axisymmetric non-stationary oscillations of a round plate supported by a one-sided round base were considered in two ways of fixing its contour, namely, when it is tightly clamped and freely supported. It was assumed that the linearly elastic base resists only compression and does not perceive stretching. It is shown that for certain durations of the transverse force pulse in time, the amplitude of the deflection of the middle of the plate in the direction of action of the external pulse can be smaller than the amplitude of the deflection in the opposite direction. At the same time, in the second case, there is no contact of the plate with the base. It has been proven that this dynamic effect of the asymmetry of the elastic characteristic of the system also applies to bending moments and is more clearly manifested when the contour is freely supported than when it is tightly clamped. For rectangular and sinusoidal pulses, closed-loop solutions of the equations of motion of the plate during its contact with the base and after separation from the base were constructed. Compact formulas were derived for calculating the amplitudes of positive and negative deflections in both directions from the zero position of static equilibrium. Formulas have been obtained for calculating the time it takes for the plate to obtain extreme deflection values, which is achieved due to the selection of a special axisymmetric distribution of dynamic pressure on the plate. Under such a load, the plate simultaneously detaches from the base at all points, except for the contour points, which reduces the nonlinear boundary value problem to a sequence of two linear problems. Numerical integration of the differential equation was carried out to check the reliability of the constructed analytical solutions. Adequacy of the model was proven for the following values of initial parameters: modulus of elasticity, 2.1·1011 Pa; the Poisson ratio of the plate material, 0.25; plate thickness, 7...10 mm; the maximum pressure on the plate, 4·103 Pa; the bending stiffness of the plate, 6402.6667 N·m. [ABSTRACT FROM AUTHOR]

The analysis of resource-saving technologies of cultivation and refinement of agricultural crops confirmed that the use of PSS pneumatic sorting tables allows to somewhat reduce the costs of cleaning and sorting. However, the imperfection of their designs and uneven grain supply reduces the effectiveness of their use. Therefore, the purpose of the research was to improve the quality of post-harvest processing of grain crops, the development of a rotary feeder. To achieve this goal, research methods and techniques have been developed. A pneumatic sorting table equipped with a three-blade rotary feeder with an outer diameter of 80 mm with straight blades located at an angle of 120 degrees has been developed. The process of grain flow motion in the hopper was studied and dependencies were established to determine grain motion in the hopper, the time of grain motion in the area under consideration and the speed of grain motion at the exit from the hopper, which was 1.167 m/s. The equations of motion of the blades for the outer and inner diameter of the rotary feeder are established, according to which the actual coordinates of their motion and displacement of the shaft axis of the rotary feeder from its original position are calculated. Calculations have determined that with an outer diameter of 0.08 m of the rotary feeder, grain velocity of 1.02 m/s, an angular velocity of 2.9 s-1, the displacement of the shaft axis of the rotary feeder from its original position at a 360 degree rotation angle will be 160 mm. This will reduce the unevenness of grain supply, and grain shattering, increase laboratory and field germination, improve the content of the output groups of full-fledged grain and, consequently, improve the quality of post-harvest processing of grain crops by a developed pneumatic sorting table equipped with a three-blade rotary feeder.

From year to year, the agricultural sector of the economy of the Russian Federation is faced two tasks: the first is harvesting grain crops at a short stated agrotechnical time, and the second – to preserve the quality of food and seed grains until the moment of product sale or sowing. One of the most effective ways to preserve the quality of food and seed grains is its cleaning and sorting. They are performed by pneumatic sorting tables of periodic and continuous operations type. In our country, the most common types of tables are PSS-0.2, PSS-2.5, PS-10, TDV 150. They have a classic scheme of pneumatic systems, vibration tables with decks and their drive mechanisms. Their disadvantages include the impossibility of uniform grain supply and increased threshing at the outlet due to the lack of grain supply devices in the hoppers, which reduces the quality of cleaning and sorting. To eliminate the identified shortcomings, we have developed, manufactured and tested a pneumatic sorting table with a rotary feeder. At first, the best type of rotary grain feeder was specified, which turned out to be a three-bladed rotary feeder with a grain supply of 0.45 kg/s and a non-uniformity of supply of 12.5%. Then, comparative studies were carried out for the chosen type of rotary feeder and the quality indicators of the technological process were determined. We compared the developed pneumatic sorting table, equipped with a three-blade rotary feeder, to the base table PSS-0.2. It was found that when cleaning the grain of winter soft wheat of "Lgovskaya 8" variety (thousand grain weight — 46.4 g, moisture content — 14.2%, and density — 1.6 g/cm3), the studied device reduces the grain crushing by 0.06 % and non-uniformity of supply (11.5%). Also, it increases the laboratory and field germination (2% and 5%, respectively), the content of the most valuable output groups III and IV by 21.2% with a slight decrease in supply by 0.01% and productivity per hour of main operating time 0.04 t/h Thus, the possibility of using the rotary feeder in pneumatic machines is proved.

In a grain pile there is material other than grain including poisonous ergot sclerotia. Grain and sclerotia of ergot by linear dimensions and speed of soaring have similar characteristics. Complete separation of grain from ergot by these properties in a single process is impossible. Cleaning seeds from ergot sclerotia with the specific mass less than the specific mass of grain is possible in a salt solution. To mechanize the separation of ergot sclerotia from rye seeds by the wet method, there is an urgent need in the development of an appropriate device. Under study was an immersion in water (ρzh = 1.0∙103 kg/m3 ) and aqueous solutions of sodium chloride (NaCl) with a specific mass ρzh = 1.09∙103 and 1.15∙103 kg/m3 of individual rye grains with their specific mass ρz = 1.2...1.5∙103 kg/m3 , length lz = 5.0...10.0 10-3 m, width в = 1.4...3.6∙10-3 m and thickness δ = 1.2...3.5∙10-3 m. Theoretical studies were carried out on the basis of mathematical modeling methods using the laws of hydrodynamics, which were confirmed by experimental studies with winter rye grains of the Falenskaya 4 variety with a specific mass ρz = 1.1...1.3 103 kg/m3 , length lz = 5.0...8.0∙10-3 m, width в = 1.4...3.6∙10-3 m and thickness δ = 1.2...3.5∙10-3 m. It has been established that the calculated values of the immersion velocity of cylindrical kernels and spheroidal kernels in comparison with the experimental values in water (ρzh = 1.0∙103 kg/m3 ) is not more than 2%, and in aqueous solutions of sodium chloride (NaCl) the specific mass ρzh = 1.09∙103 and 1.15∙103 kg/m3 – 7 and 10%, respectively. This approach to determining the speed of immersion of grain in liquid can be used in the development of the machine for cleaning grain according to specific mass using wet method to substantiate its structural and technological parameters.